Tories



M 8 2 R m w M L M E R w C m d e A Nl m F May 5, 1931.

METHOD OF AND MEANS FOR DETERMINING CYCLIC //vv/v7'0/?: ART/1w? C. KELLER ATTORNEY Patented may .5, 19st UNITE saTES ARTHUR G. KELLER, NEW YORK, N. Y.,

PATENr Erica ASSIGNOB T0 BELL TEEPHON'E LABORA- TORIES, INCORPORATED, OF YORK, N. Y A CORPORATION OF NEW YO men or AND rams non nn'rnnmmme CYOLIC vanmrrous m a norarme uni/Inna Application filediebruary 10, 1928. Serial 1%. 253,251.

This invention relates to a method of and apparatus for determining variations in the movement of a rotating member and its object is to provide a method of and means by which any variation in the turning movement of a rotating member in one complete cyclic rotation may be determined.

To accomplish this object movement of the rotating member under test is employed to 19 cause generation of an electromotive force of a predetermined Wave form which may be recorded and any variation in the cyclic rotatitn of the member noted by noting the variations of the wave from the predetermined form.

In general the apparatus employed to accomplish the desired object comprises a magnet structure and an electrical pick-up coil one of which may be carried by the rotating member and the other held stationary relative thereto so that the magnetic field of the magnet structure is cut by the pick-up coil duejto the turning movement of the rotating member and an electromo'tive force is suitable apparatus and any variations in the movement of the rotating member under test determined.

The electrical current generated in the pick-up coil may be employed to produce a tone in a telephone receiver or other suitable sound producing device or the pick-up coil may be suitably connected to an oscillograph by which a visible record will be made of the wave produced in the coil or the pick-up coil may be connected to a harmonic analyzer b which the wave produced will be analyze as to its various com onents.

In the preferred form of this invention a magnet structure is attached to and rotated by the member under test past a stationary inductor coil and the magnet structure is so designed that the volta e induced in the coil will be of pure sinusoi al form, when there is" no variation in'the cyclic rotation of the member under test.

Two designs of apparatus by which the object of this inventlon may be accomplished are shown in the attached drawings in which so 1 is a plan view of a magnet structure generated which may benoted or recorded by which may be attached to a rotatable shaft and Fig. 2 is a magnet structure which may be placed on a fiat rotatable surface such as the turntable of a phonograph. Fig. 3 is a schematic showing in conventionaform,

means by which notation may be made of the shaped with the open ends adjacent. The

cup-shaped pole piece 3 is or even depth all around while the cup-shaped pole piece 4 is of uneven depth being so shaped that when placed adjacent the pole piece 3, a varying air gap is obtained. Held stationary in the air gap between the pole ieces is an inductor coil 5 with leads 6 and i which may be attached to a telephone receiver or other recording device.

When the shaft 2 and the magnet structure, comprising the permanent ma et 1 and the pole pieces 3 and 4, is rotated y the shaft under test, the lines of force in the rotating magnetic field are cut by the inductor coil 5 and an electromotive force is induced in the inductor coil 5 which will produce a tone in a telephone receiver or will actuate whatever recording device it is connected with. The magnet structure is so designed that for an unvarying cyclic rotation of the shaft a sound of a predetermined tone will,

be produced by the receiver or a wave of predetermined form will be produced in the recording device.

In Fig. 2,8 is a flat disc of brass or other nonmagnetic material with a central aperture 9 adapted to receive a shaft or pin such as the center pin of a phonographic turntable. Encircling and attached to the nonmagnetic disc 8 is a ring shaped permanent magnet 10 and encircling and attached to the permanent magnet 10 is a soft iron ring 11 till I of varying width. Placed closely adjacent structure comprising the encircling ring shaped permanent magnet 10 and the encircling soft i-ron ring 11 is rotated by turningof the phonographic turntable. or the rotatablestructure under test, the air gap between the soft iron ring 11 and the stationary inductorcoil 12 is varied, due to the varying width of the soft iron ring 11, and an electromotive force is induced in the inductor coil 12.

The soft'iron ring 11 is so shaped that the electromotive force induced in the inductor coil 12 will be of a predetermined wave form if there is no variation in the cyclic rotation of the member under test. The electromotive force induced in the inductor coil 12 will, if the coil is in circuit connection with a telephone receiver, produce in the receiver a note of a predetermined tone. If the inductor coil 12 is in circuit connection with a recording device designed to make visible records, a record of predetermined wave form will be recorded.

It may be found desirable to amplify the 7 wave induced in the inductor [coil 5 or 12,

whichever apparatus is bein used in making the test, so that the tone 1n the telephone receiver may be more easily detected or the recording apparatus properly actuated. It may be found desirable to make an analysis of the wave produced as to its various components or it may be desired that a picture of the wave be made.

Means for accomplishing the above men tioned facilities are conventionally illustrated in Fig. 3 in which by a switching arrangement 15 the inductor 'coil 5 or 12 may be connected to either an amplifier 16 placed between the coil 5 and a telephone receiver to produce therein a more audible tone or the coil may be connected through switch 15 to an electrical harmonic analyzer 17 which will analyze the wave as to its various components. Also through the. switch 15 the inductor coil 5 may be connected to an oscillograph 18 which will produce on a suitably scaled chart or screen apicture of the form of wave induced in the coil. From the wave picture obtained on the oscillograph 18, analysis of the wave as to its various components may also be obtained by use of a mechanical harmonic analyzer illustrated at 19.

' Diflerent types of magnet structures and difierent combinations of magnet structures and induction coils than those shown in the attached drawings may clearly be employed in determining variations in the movement of a rotating member during a complete cycle of rotation. This invention therefore is considered not to be limited to the particular construction shown but to include such other means for determining cyclic variations in a rotating member as come within the scope of the followinsr claims. What is claimed is 1 Apparatus for determinin variations in the cyclic rotation of a rotating member comprising a magnet structure to be attached to the rotating member, an electrical pick-up coil and apparatus brought into circuit connection therewith for visibly indicatingthe voltage waves induced in the electrical pickup coil, the said magnet structure being so formed that for an unvarying cyclic rotation of the magnet structure a voltage wave of approximately pure sinusoidal form will generated. 1 v

2. Apparatus for determining variations in the cyclic rotation of a rotatm member comprising a magnet structure to ecarried by the rotating member, an electrical pickup coil placed in close proximity to the magnet structure and voltage wave analyzing apparatus in circuit connection with the electrical pick-up coil, thesaid magnet structure being so formed that a varying air-gap is obtained between the magnet structure and the electrical pick-up coil. and the voltage wave induced in the electrical pick-u coil for one unvarying cyclic movement 0 the magnet structure will be of approximately true smusoidal form.

3. Apparatus for determining variations in the cyclic rotation of a rotatlng member comprising a magnet structure to be carried by the rotating member, an electrical pick up coil held. within thefield of the magnet structure and a paratus in circuit connection with the electrlcal ick-up coil to visibly indicate the form 0 the voltage wave generated, said magnet structure being so formed I that a gradual variation inthe airrap between the magnet structure and co'? is obtained during one cyclic rotation of the rotatin member and for one unvarying cyclic rotatlon a voltage wave of ap roxlmately pure sinusoidal form is produce in the electrical pick-up coil. v v

4. Apparatus for determinin variations in the cyclic rotation of a rotatlng member comprising a cylindrical magnet to be attached to the rotating member, cup-shaped pole pieces attached to the ends of the cylindrical magnet, an air-gap between the pole.

ieces, an electrical pick-up coil located with- 1n the air-gap and apparatus in circuit connection with the electrical pick-up coil for visibly indicating the form of the volta e wave produced, the said cup-shaped p0 e pieces so formed that the air-gap between them is of constant varying width through- "out.

Ill

111 name this 3rdda of Februa 1928.

y ARiHUR-c.

sists in moving by said member a Portion of a magnet system having a constant v air-gap between the magnet and a and generating a voltage wave 0 sinusoidal form, recording the form of the wave roduced and comparing with a substantially true sine wave to determine at what points there was any variation. in the cyclic movement.

In witness whereof, I hereunto subscribe LLER.

y ick-up col 

